Particle Acceleration by Pickup Process Upstream of Relativistic Shocks

Masanori Iwamoto, Takanobu Amano, Yosuke Matsumoto, Shuichi Matsukiyo, Masahiro Hoshino

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Particle acceleration at magnetized purely perpendicular relativistic shocks in electron-ion plasmas is studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor γ 1 ≫ 1 are known to emit intense electromagnetic waves from the shock front, which induce electrostatic plasma waves (wakefield) and transverse filamentary structures in the upstream region via stimulated/induced Raman scattering and filamentation instability, respectively. The wakefield and filaments inject a fraction of the incoming particles into a particle acceleration process, in which particles are once decoupled from the upstream bulk flow by the wakefield, and are picked up again by the flow. The picked-up particles are accelerated by the motional electric field. The maximum attainable Lorentz factor is estimated as for electrons and for ions, where α ∼ 10 is determined from our simulation results. α can increase up to γ 1 for a weakly magnetized shock if γ 1 is sufficiently large. This result indicates that highly relativistic astrophysical shocks such as external shocks of gamma-ray bursts can be an efficient particle accelerator.

Original languageEnglish
Article number108
JournalAstrophysical Journal
Volume924
Issue number2
DOIs
Publication statusPublished - Jan 10 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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